This application relates generally to the alignment of optical elements. More specifically, this application relates to the alignment of optical elements using lithographic processes.
There are a number of applications in which optical elements need to aligned. Of particular interest are laser and detector optical subassemblies, including transmit optical subassemblies (“TOSAs”) and reflect optical subassemblies (“ROSAs”), which typically require high alignment accuracy. Laser emitters often require especially high position accuracy, with a tolerance much less than 1 μm to achieve high-efficiency coupling. This is because waveguide-based edge emitting laser diodes, and sometimes light-emitting diodes, typically have optically active regions emitting beam diameters on the order of 1 μm high by 3 μm wide. Such a source accordingly needs to be imaged rather precisely onto an optical element like a lens, fiber, or other optical structure to within submicron precision. Other laser sources such as Vertical Cavity Surface Emitting Lasers (“VCSELs”) have beams on the order of 5 μm and still require precision alignment.
Alignment of distinct physical parts may be an expensive procedure and must take into account a number of different issues when coupling light into or out of an optical package with high efficiency. The optical beam must be formed efficiently to match the beam shape between the parts to be coupled. Mechanical alignment of the parts to high accuracy for high-efficiency coupling often requires active feedback from optical beams traversing the part to measure the alignment position properly. Such a procedure usually requires one or more optical components being powered to emit or detect light and securing them while aligned. Such a power-on active alignment process is difficult if the part being activated is the one being manipulated to achieve the alignment. In order to achieve alignment in these ways, it is also generally necessary to provide a rigid structure that remains stable with high accuracy over time, temperature, and external stresses.
There is accordingly a need in the art form methods of aligning optical elements that accounts effectively for these issues.